/* MD5
 converted to C++ class by Frank Thilo (thilo@unix-ag.org)
 for bzflag (http://www.bzflag.org)
 
   based on:
 
   md5.h and md5.c
   reference implementation of RFC 1321
 
   Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
rights reserved.
 
License to copy and use this software is granted provided that it
is identified as the "RSA Data Security, Inc. MD5 Message-Digest
Algorithm" in all material mentioning or referencing this software
or this function.
 
License is also granted to make and use derivative works provided
that such works are identified as "derived from the RSA Data
Security, Inc. MD5 Message-Digest Algorithm" in all material
mentioning or referencing the derived work.
 
RSA Data Security, Inc. makes no representations concerning either
the merchantability of this software or the suitability of this
software for any particular purpose. It is provided "as is"
without express or implied warranty of any kind.
 
These notices must be retained in any copies of any part of this
documentation and/or software.
 
*/
 
#pragma once

#include <cstring>
#include <iostream>

// Constants for MD5Transform routine.
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

namespace Digest
{
	// a small class for calculating MD5 hashes of strings or byte arrays
	// it is not meant to be fast or secure
	//
	// usage: 1) feed it blocks of uchars with update()
	//      2) finalize()
	//      3) get hexdigest() string
	//      or
	//      MD5(std::string).hexdigest()
	//
	// assumes that char is 8 bit and int is 32 bit
	class MD5
	{
	public:
		typedef unsigned int size_type; // must be 32bit
 
		MD5()
		{
			init();
		}
		
		MD5(const std::string& text)
		{
			init();
			update(text.c_str(), text.length());
			finalize();
		}
		// MD5 block update operation. Continues an MD5 message-digest
		// operation, processing another message block
		void update(const unsigned char input[], size_type length)
		{
			// compute number of bytes mod 64
			size_type index = count[0] / 8 % blocksize;
 
			// Update number of bits
			if ((count[0] += (length << 3)) < (length << 3))
				count[1]++;
			count[1] += (length >> 29);
 
			// number of bytes we need to fill in buffer
			size_type firstpart = 64 - index;
 
			size_type i;
 
			// transform as many times as possible.
			if (length >= firstpart)
				{
					// fill buffer first, transform
					memcpy(&buffer[index], input, firstpart);
					transform(buffer);
 
					// transform chunks of blocksize (64 bytes)
					for (i = firstpart; i + blocksize <= length; i += blocksize)
						transform(&input[i]);
 
					index = 0;
				}
			else
				i = 0;
 
			// buffer remaining input
			memcpy(&buffer[index], &input[i], length-i);
		}
 
		//////////////////////////////
 
		// for convenience provide a verson with signed char
		void update(const char input[], size_type length)
		{
			update((const unsigned char*)input, length);
		}		
		
		MD5& finalize()
		{
			static unsigned char padding[64] = {
				0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
				0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
				0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
			};
 
			if (!finalized) {
				// Save number of bits
				unsigned char bits[8];
				encode(bits, count, 8);
 
				// pad out to 56 mod 64.
				size_type index = count[0] / 8 % 64;
				size_type padLen = (index < 56) ? (56 - index) : (120 - index);
				update(padding, padLen);
 
				// Append length (before padding)
				update(bits, 8);
 
				// Store state in digest
				encode(_digest, state, 16);
 
				// Zeroize sensitive information.
				memset(buffer, 0, sizeof buffer);
				memset(count, 0, sizeof count);
 
				finalized=true;
			}
 
			return *this;
		}

		std::string digest() const
		{
			std::string out;
			for (int i=0; i<16; ++i)
				out+=_digest[i];
			
			return out;
		}
		
		std::string hexdigest() const
		{
			if (!finalized)
				return "";
 
			char buf[33];
			for (int i=0; i<16; i++)
				sprintf(buf+i*2, "%02x", _digest[i]);
			buf[32]=0;
 
			return std::string(buf);
		}
		
		friend std::ostream& operator<<(std::ostream& out, MD5 md5)
		{
			return out << md5.hexdigest();
		}
 
	private:
		void init()
		{
			finalized=false;
 
			count[0] = 0;
			count[1] = 0;
 
			// load magic initialization constants.
			state[0] = 0x67452301;
			state[1] = 0xefcdab89;
			state[2] = 0x98badcfe;
  state[3] = 0x10325476;
		}
		
		typedef unsigned char uint1; //  8bit
		typedef unsigned int uint4;  // 32bit
		enum {blocksize = 64}; // VC6 won't eat a const static int here
 
		void transform(const uint1 block[blocksize])
		{
			uint4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];
			decode (x, block, blocksize);
 
			/* Round 1 */
			FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
			FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
			FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
			FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
			FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
			FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
			FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
			FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
			FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
			FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
			FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
			FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
			FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
			FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
			FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
			FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */
 
			/* Round 2 */
			GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
			GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
			GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
			GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
			GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
			GG (d, a, b, c, x[10], S22,  0x2441453); /* 22 */
			GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
			GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
			GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
			GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
			GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
			GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
			GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
			GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
			GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
			GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */
 
			/* Round 3 */
			HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
			HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
			HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
			HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
			HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
			HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
			HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
			HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
			HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
			HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
			HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
			HH (b, c, d, a, x[ 6], S34,  0x4881d05); /* 44 */
			HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
			HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
			HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
			HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */
 
			/* Round 4 */
			II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
			II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
			II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
			II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
			II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
			II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
			II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
			II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
			II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
			II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
			II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
			II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
			II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
			II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
			II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
			II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */
 
			state[0] += a;
			state[1] += b;
			state[2] += c;
			state[3] += d;
 
			// Zeroize sensitive information.
			memset(x, 0, sizeof x);			
		}
		
		static void decode(uint4 output[], const uint1 input[], size_type len)
		{
			for (unsigned int i = 0, j = 0; j < len; i++, j += 4)
				output[i] = ((uint4)input[j]) | (((uint4)input[j+1]) << 8) |
					(((uint4)input[j+2]) << 16) | (((uint4)input[j+3]) << 24);
		}
		
		static void encode(uint1 output[], const uint4 input[], size_type len)
		{
			for (size_type i = 0, j = 0; j < len; i++, j += 4) {
				output[j] = input[i] & 0xff;
				output[j+1] = (input[i] >> 8) & 0xff;
				output[j+2] = (input[i] >> 16) & 0xff;
				output[j+3] = (input[i] >> 24) & 0xff;
			}
		}
		
 
		bool finalized;
		uint1 buffer[blocksize]; // bytes that didn't fit in last 64 byte chunk
		uint4 count[2];   // 64bit counter for number of bits (lo, hi)
		uint4 state[4];   // digest so far
		uint1 _digest[16]; // the result
 
		// low level logic operations
		static inline uint4 F(uint4 x, uint4 y, uint4 z)
		{
			return x&y | ~x&z;
		}
		
		static inline uint4 G(uint4 x, uint4 y, uint4 z)
		{
			return x&z | y&~z;
		}
		
		static inline uint4 H(uint4 x, uint4 y, uint4 z)
		{
			return x^y^z;
		}
		
		static inline uint4 I(uint4 x, uint4 y, uint4 z)
		{
			return y ^ (x | ~z);
		}

		static inline uint4 rotate_left(uint4 x, int n)
		{
			return (x << n) | (x >> (32-n));
		}
		
		static inline void FF(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
		{
			a = rotate_left(a+ F(b,c,d) + x + ac, s) + b;
		}
		
		static inline void GG(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
		{
			a = rotate_left(a + G(b,c,d) + x + ac, s) + b;
		}
		
		static inline void HH(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
		{
			a = rotate_left(a + H(b,c,d) + x + ac, s) + b;
		}

		
		static inline void II(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
		{
			a = rotate_left(a + I(b,c,d) + x + ac, s) + b;
		}
		
	};
 
	/* std::string md5(const std::string str) */
	/* { */
  /*   MD5 md5 = MD5(str); */
 
  /*   return md5.hexdigest();		 */
	/* } */

};
